1. Field of the Invention
This invention relates to methods and apparatus for the manufacture of methane gas. More particularly, it concerns the utilization of sewage sludge or other organic wastes as a source material for methane gas plus fertilizer and the use of solar heating to reduce the cost of production of the methane gas.
2. Description of the Prior Art
It is well known that methane gas can be generated by bacterial decomposition of organic materials. Because it is produced in nature in this manner in large amounts, particularly in swampy areas, it is commonly called marsh gas. This natural process has recently created some serious problems in suburban residential areas located over or adjacent to trash landfills which are beginning or decay on a massive scale and produce dangerous quantities of methane gas (see "Washington Post", Apr. 4, 1976, p. 1, article entitled "Methane: Richmond's Peril").
The United States generates millions of pounds of trash and organic waste daily, much of which is continued to be disposed of in so-called sanitary landfills. The disposal of such waste and a potent source of valuable energy could be obtained if the bacterial decomposition of organic waste to produce methane gas could be preformed in a controlled manner which would be economically acceptable.
One of the problems in producing methane gas via bacterial action is the heating of large quantities of material to promote bacterial decomposition. Of course, solar energy offers an opportunity for cheap heat and many systems have been devised in an attempt to utilize solar energy for various heating purposes. The following U.S. Patents are representative of disclosures of such systems: U.S. Pat. Nos. 1,753,227; 2,933,885; 1,933,213; 3,048,375.
Notwithstanding the great amount of study and work devoted to solar energy heating and utilization, solar heating has not been extensively used as a major source of reaction heat in conducting continuous chemical processes because of its intermittent availability as well as the high cost of construction and operation of many of the known type of solar heating devices. The production of methane gas together with a desireable way to dispose of organic waste would be promoted if solar energy could be utilized in a practical manner on a commercial scale for the bacterial decomposition of organic waste into methane gas.